1. Field of the Invention
The present invention relates, in general, to a method and system for assessing the risks and prognoses associated with a given course of medical treatment of neurological tumors, such as brain tumors. In particular the present invention relates to a method and system for assessing the risks and prognoses associated with a given course of medical treatment of neurological tumors, such as brain tumors, wherein that given course of medical treatment spans multiple medical subspecialties.
2. Description of Related Art
Anatomically, the brain consists of three main structures: the central brain stem, the cerebrum, and the cerebellum. Each such structure contains within it many other defined regions and/or substructures associated with specific brain function(s).
The brain stem is divided into substructures. Such substructures include the thalamus, hypothalamus, and medulla oblongata. The thalamus is the relay station for incoming sensory signals and outgoing motor signals passing to and from the brain stem and cerebrum. The hypothalamus regulates or is involved directly in the control of eating, drinking, temperature regulation, sleep, emotional behavior, sexual activity, and visceral functions. The medulla oblongata regulates and controls cardiac, vasoconstrictor, and respiratory functions, as well as other reflex activities, including vomiting.
The cerebrum is the largest part of the human brain and is divided into several substructures. These substructures include, among others, the right and left cerebral hemispheres, each of which is divided by fissures and gyri (convolutions) into five lobes: the frontal, parietal, temporal, occipital, and insula lobes.
Many distinct brain functions have been associated with different regions and substructures within the cerebrum. These regions and substructures include the following. The somatomotor area, located just in front of what is known as the central fissure of one cerebral hemisphere, is responsible for nearly all voluntary movement of body muscles. The somatosensory area, which is responsible for touch and taste, which is located just behind what is known as the central fissure of one cerebral hemisphere. The region of the cortex responsible for hearing is located in the upper, or superior, convolution of the temporal lobe of one cerebral hemisphere. The visual cortex, the region responsible for seeing, is located in the occipital lobe of one cerebral hemisphere. The olfactory area, the region responsible for smell, is located in the front, internal portion of the temporal lobe. Broca's area responsible for the muscle movements of the throat and mouth used in speaking, is located just beneath the motor area. The understanding of speech and reading has been associated with areas between the auditory and visual areas. The frontal area of the human cortex is responsible for awareness, intelligence, and memory.
The cerebellum is essential to the control of movement of the human body in space. It acts as a reflex center for the coordination and precise maintenance of equilibrium. Voluntary muscle tone--as related to posture, balance, and equilibrium--is similarly controlled by the cerebellum. All motor activity depends on the cerebellum.
The foregoing identified functional areas are just a fraction of those areas of the brain with which a specific function has been associated. Eloquence can be defined to be the quality of forceful or persuasive expressiveness. Consequently, areas of the brain identified with the expression of functions will be referred to herein as eloquent areas. Damage to "eloquent" areas of the brain typically results in severe impairment or elimination of the function(s) associated with such damaged eloquent area (e.g., severe damage to the medulla oblongata structure usually results in immediate death).
A brain tumor is an abnormal growth, swelling, or enlargement in the brain. There are many types of brain tumors such as those arising from the brain itself (e.g., astrocytoma, glioblastoma, oligodendroglioma, ependymoma), those arising from the brains coverings, or meninges, (e.g., meningiomas, pituitary tumors, pineal tumors), or those arising from nerves at the base of the brain (e.g., acoustic neuromas, schwannomas), and even tumors arising from outside the brain (metastatic brain tumors). This last case occurs when cancer cells travel through the bloodstream and lodge in the brain.
Brain tumors can be malignant or benign. A malignant tumor is one that is actively destroying surrounding brain cells. A benign tumor is a mass or swelling that is growing, but is not destroying the surrounding brain cells. While a benign tumor in other organs is not ordinarily cause for alarm, a benign brain tumor is cause for alarm.
The brain is encased in the cranium. The cranium is a dome-like vault of bone and cartilage that is essentially unyielding. Surrounding the brain is cerebrospinal fluid under a pressure, which supports the brain and protects it from injury. Cerebrospinal fluid is essentially incompressible, and thus the introduction of a tumor, even a benign one, into the cranial vault will require compression of the structures which can be compressed: the cells of the brain. Such compression ultimately will result in brain injury, and thus even benign tumors must be removed as quickly as possible. Thus, even a benign tumor can cause severe damage and must be removed quickly and in its entirety. Thus, irrespective of whether a brain tumor is malignant or benign, an active course of treatment must be engaged in to remove the tumor.
Unfortunately, this is easier proposed than done, for brain tumors are significantly different from other types of tumors, and hence are uniquely difficult to remove. There are several reasons for this, but perhaps the most significant is that brain tumors are in/on the brain, and thus reaching and removing the tumor with surgical instruments gives rise to the risk that eloquent brain areas will be damaged in either the process of reaching the tumor or removing it. A second reason is that brain tumors aren't like ordinary tumors: brain tumors are polyclonal, which means that what appears to be one tumor is actually many (sometimes over a thousand) tumor clones co-located in one area. Consequently, true tumor margins do not exist and consequently total removal by local therapy (surgery, radiation, heat, cold, etc.) is not possible. A third reason is that the brain is separated from the blood-stream by the blood-brain barrier, and consequently many blood-born chemotherapeutic agents cannot reach the brain via the blood-stream. A fourth reason is that many brain tumor cells live in a low oxygen environment (hypoxic), and it has been found empirically that these hypoxic cells are: (1) radio-resistant; (2) often chemotherapy resistant; and (3) far from the blood supply. Thus, brain tumors prove to be exceedingly difficult to treat as compared with other tumors, as the following simple example will make clear.
Imagine that a particular tumor weighs about 100 grams. Consider the following: 100 gm of tumor typically has approximately 100 billion cells. Because a typical tumor can double in size and volume in a matter of weeks, from a course of treatment standpoint it makes sense to decrease the size of the mass of the tumor right away. Surgery is the preferred way of radically reducing the volume of a tumor, removing anywhere from 80-90% of the tumor mass. Recent advances in surgical technologies have aided in the removal of brain tumor tissue with a newer, higher net percentage tumor reduction of 90-99%. These include computer assisted stereotactic surgery, laser instrumentation (carbon dioxide, argon, and Yag), ultrasonic aspiration, operative phototherapy, focused beam radiotherapy proton beam radiation--the Gamma knife, linear accelerator--the "X-knife," brachytherapy--radiation seeds implanted into the tumor bed, cryotherapy, thermal therapy, ultrasonic therapy, phototherapy, drug and immunotherapies injected locally into the tumor bed via an Omaya reservoir, intraarterial therapy--selective exposure of involved brain via angiography.
The foregoing percentage removals sound good until one considers the following: 90% removal of tumor (100,000,000,000 cells), leaves 10 billion cells. Even if one assumes a 99% removal of tumor (100,000,000,000 cells), this still leaves 1 billion cancer cells in the brain.
Thus, no matter how good the local surgical therapy is, in the foregoing simple example it is clear that the patient is still left with at least 1 billion tumor cells. Consequently, brain tumor treatment typically consists of following up the surgical therapy with radiotherapy and/or chemotherapy. Thus, any given course of treatment of brain tumors usually involves, at a minimum, some form of surgical intervention, plus some form of chemical therapy, plus some form of radiation therapy. There are significant risks associated with each form of treatment, as well as with the course of treatment considered as a whole.
With respect to surgical intervention, one of the most significant risks is that of damage to the above-described eloquent brain areas. These risks are often closely related to the path taken by the surgical instruments from the outside of the cranium to the tumor within the brain, the location, the size of the tumor at the time of surgery, and the percentage of the tumor that is ultimately removed. For example, one path to a tumor might have associated with it the risk of damage to the brain centers controlling feeling in one area of the body, while another path might have the risk damage to the brain centers wherein are contained the patient's individual identity. Alternatively, one path might have associated with it a risk of loss to a major eloquent area, while another path might have associated with it damage associated with a number of more minor surgical areas.
With respect to radiation therapy, it is known that the dosage needed to cure all malignant brain tumors is approximately 12,000 Rads. However, such a high dosage is also extremely neurotoxic and therefore deadly. Consequently, the medical community consensus is that radiation doses of 5,000 to 6,000 rads is the standard of care that should be provided by the reasonably prudent practitioner in this area. These doses have "acceptable" brain toxicity rates. Unfortunately, only the very, very rare tumor is adequately treated with this radiation dosage. Also, different types of cells have more or less susceptibility to radiation therapy (e.g., hypoxic cells being relatively less sensitive to radiation). Thus, a significant risk associated with radiotherapy is the risk that the tumor will not respond.
Furthermore, if the radiotherapy is via a directed beam of radiation, such radiation will tend to kill everything in the beam's path, so risks of damage similar to those associated with a surgical path are also associated with the radioactive path.
With respect to chemotherapy, an extraordinary compendium of chemotherapeutic agents is under constant development at present, but as has been discussed, such agents have limited use due to the blood-brain barrier, and thus one risk associated with chemotherapy is the risk of not reaching the tumor. Another risk is that such therapies themselves tend to make the patient very sick, oftentimes wiping out the immune system of the patient in to course of killing the tumor. Furthermore, selectivity (killing tumor cells while sparing healthy cells) is also a risk with chemotherapy. It is possible to surgically place such chemotherapeutic agents, but such placement moves one right back into the risks associated with therapy.
As has been discussed, a given course of treatment for a brain tumor has associated with it typically at least three major components: surgery, radiation, and chemotherapy. Furthermore, as has been discussed, each component associated with a given course of treatment has associated with it several risk factors. Consequently, the risks and prognoses associated with a given course of medical treatment are dependent upon the individual risks associated with each component of the treatment.
Thus, possible courses of medical treatments of brain tumors have associated with them a dizzying array of variables, such as, to name just a few, the possible surgical paths to be taken to the tumor and the risks associated with same, the possible radiation paths to be traveled to the tumor and the risks associated with same, and the effectiveness of various radiation and chemotherapy associated with the tumor type and its locations, as well as side effects associated with such radiation therapy and chemotherapy.
Current practice is for the medical personnel (e.g., surgeons, oncologists, hematologists, etc.) to meet with the patient and outline various courses of treatments and possible risks and prognoses associated with such courses of treatment. Typically, this assessment is broken down into pre-surgical and post-surgical phases. In the pre-surgical phase, the risks and prognoses are basically done in an idealized text-book type setting. In the post-surgical phase, the risks and prognoses are done with respect to what actually occurred during surgery, as well as what was actually found during surgery related to the location, size, composition, and percentage of the actual tumor removed during the surgery.
Even in the rather abstract discussion set forth above, it is clear that there are a dizzying array of variables, spanning several disjoint medical subspecialties, associated with tumor treatments. Consequently, the current practice involved in the choice of a given course of treatment is intuitive more than anything else, in that each medical professional involved sets forth his perspective of the risks and benefits associated with different phases of particular courses of treatments, and then the lead surgeon in conjunction with the patient chooses a given course of treatment, more typically by intuition and back of the envelope informal calculations than by anything else.
It is undeniable that intuition plays a large and indispensable part medical treatment. However, there are instances where the exercise of such intuition is appropriate and instances where it is not. Such intuition is appropriate where a decision process truly can't be quantified and the choice to be made resolves to a manner of human judgement, such as a choice among given medical treatments when all the variables are known. However, such intuition is inappropriate where virtually all variables involved can be quantified, but the number and possible permutations of those variables exceeds the ability of the human brain to practicably process them.
Given the fact that the majority of factors associated with the treatment of brain tumors can be quantified, it is apparent that a need exists for a method and system which will allow the quick and efficient assessment of the various risks and prognoses associated with various courses of medical treatment of brain tumors, especially when such courses of treatment span/encompass many different and varied medical subspecialties.
It is therefore apparent that a need exists for a method and system which will provide artificial intelligences capable of assisting with assessing the risks and prognoses associated with the treatment of brain tumors, especially when such treatment spans several medical subspecialties.